Immune infiltration and PD-L1 expression in the tumor microenvironment are prognostic in osteosarcoma

Abstract

Osteosarcoma patient survival has remained stagnant for 30 years. Novel therapeutic approaches are needed to improve outcomes. We examined the expression of Programmed Death Ligand 1 (PD-L1) and defined the tumor immune microenvironment to assess the prognostic utility in osteosarcoma. PD-L1 expression in osteosarcoma was examined in two patient cohorts using immunohistochemistry (IHC) (n = 48, n = 59) and expression was validated using quantitative real time PCR (n = 21) and western blotting (n = 9). IHC was used to determine the presence of tumor infiltrating lymphocytes and antigen-presenting cells (APCs) in the tumor. Expression of PD-L1 was correlated with immune cell infiltration and event-free-survival (EFS). The 25% of primary osteosarcoma tumors that express PD-L1 were more likely to contain cells that express PD-1 than PD-L1 negative tumors (91.7% vs 47.2%, p = 0.002). Expression of PD-L1 was significantly associated with the presence of T cells, dendritic cells, and natural killer cells. Although all immune cell types examined were present in osteosarcoma samples, only infiltration by dendritic cells (28.3% vs. 83.9%, p = 0.001) and macrophages (45.5% vs. 84.4%, p = 0.031) were associated with worse five-year-EFS. PD-L1 expression was significantly associated with poorer five-year-EFS (25.0%. vs. 69.4%, p = 0.014). Further studies in osteosarcoma are needed to determine if targeting the PD-L1:PD-1 axis improves survival.

Increased PD-L1 and T-cell infiltration in the presence of HLA class I expression in metastatic high-grade osteosarcoma: a rationale for T-cell-based immunotherapy

“…An increased PD-1 expression on peripheral CD4 + T cells was also observed in patients with metastases, strengthening the idea that PD-L1/PD-1 axis may play a role during osteosarcoma progression [25]. Recently, Koirala et al reported the discrepancy between whole tumour sections and tissue micro-arrays as a result of the heterogeneity of PD-L1 expression in osteosarcoma, confirming our idea that this immune marker should be evaluated on whole sections [26]. Moreover, they identified PD-L1 positivity as a potential prognostic marker for poorer survival, which was not the case in our cohort.…”

The contribution of immune infiltrates and the local microenvironment in the pathogenesis of osteosarcoma

“…However, these authors observed a positive correlation with the presence of CD3 + T-lymphocytes, CD20 + Blymphocytes, CD1a + dendritic cells and CD68 + macrophages [78]. HHLA2 expression was higher in metastatic specimens than in non-metastatic samples and was correlated with metastatic disease and poor survival rate [78]. HHLA2 could then contribute to the local immunosuppression in osteosarcoma.…”

“…Recent estimation showed that Tumor-Infiltrating Lymphocytes (TILs) are detectable in 75% of osteosarcoma with a peak around 86% in metastases [78].…”

“…Then, it was proposed that TIL would represent a selected population of T-cells with a higher specific immunological reactivity against tumor cells than the non-infiltrating lymphocytes, despite of their anergy by the microenvironment (e.g. M2-TAMs, mesenchymal stem cells) or/and by cancer cells [78]. Based on this hypothesis, expanded T-lymphocytes loaded with tumor antigens were initially used in melanoma with a relative success in metastatic patients [81,82].…”

“…However obtained levels were too low in regard to the requirement for immunotherapy [83,84]. In addition, while expanded TILs had higher cytotoxic properties against allogeneic and autologous tumor cells compared to autologous blood peripheral lymphocytes ( Figure 1A), a low expression of immunomodulatory molecules on osteosarcoma cells or/and the secretion of suppressive mediators may prevent activation and expansion of these TILs [78]. This local immunosuppression has been extensively studied in the last five years.…”